Commuters have faced thick fog on their journeys to work on Monday morning, with some flights cancelled due to the bad weather.
The Met Office issued a fog alert for large parts of Southern England on Monday.
The yellow warning said that people should expect “slower journey times with delays to bus and train services”.
There is also a “chance of delays or cancellations to flights”, the forecaster said.
Heathrow airport said that poor visibility due to fog meant that it was operating with a reduced flow rate, meaning delays for passengers as the rate of planes taking off and landing was lower than normal.
British Airways cancelled 15 departure flights from the airport. The airline cited the weather in a statement, saying: “There are issues with fog in multiple areas in the UK including London.”
London City airport has advised passengers to check the status of their flight before they leave home due to the “adverse weather conditions”. Six departure flights were cancelled at the terminal.
Although the alert was only in place until 10am, parts of Southern England were still engulfed in fog past when the alert expired.
For those areas that are affected, the fog “will reduce the visibility to around 100 metres.. leading to difficult driving conditions”, the Met Office said.
The East Midlands, East of England, London and the South East, the West Midlands and Yorkshire and Humber have all been covered in a blanket of fog.
The last couple of months have been unseasonably warm and last week saw the hottest Armistice Day and Remembrance Sunday on record - with highs of 20C and 21.2C respectively.
However the balmy temperatures are likely to change soon, the Met Office predicts.
Rain will move in on Tuesday, travelling from West to East. This will be accompanied by gusts of wind, with Northern Ireland, Wales and South West England experiencing drier conditions.
Wednesday is set to be an unsettled and windy day with spells of rain.
